The present invention relates to a manually operated zero load rapid lifting hydraulic jack having a lifting arm with an integral receiver portion. When a lever is inserted into the receiver portion and the lever is pressed downward, the lifting arm axle is used as a fulcrum to drive the lifting arm upwards rapidly into a load contacting position.
A prior art hydraulic jack, such as a wheeled jack, uses a lever to engage a release valve and actuate the pumping mechanism. As well when engaged into the pumping receiver, the lever is used to position the jack under a lifting point. When the lever is used to engage the release valve to close the hydraulic circuit and then moved into the pumping receiver, the user can pump fluid from the fluid reservoir through a directional valve and then into a chamber which houses a moveable ram member by means of a directional valve, thereby causing the ram member to move at a rate dependent upon the quantity of oil displaced by the pump piston and the effective area presented by the moveable ram member. Generally, the rate at which the moveable ram member causes the lifting arm to raise is slow and gradual and not considered rapid in nature. Under no load condition the rate at which the ram member extends the lifting arm is not noticeably changed from the rate at which it travels under loaded conditions, i.e. the amount of fluid displaced by the pump piston is not increased. Operating force has increased due to the compression of the fluid within the pump and ram chambers under loaded conditions, but rate of travel has not. The user wastes time and labor in his effort to merely contact the lift point, as the pump lever must be moved up and down many times.
Patent application Ser. No. 09/146,432 and 09/766,620 (patented as U.S. Pat. Nos. 6.035.635 and 6,347,786. respectively) teach the prior art. However, these designs utilize an internal hydraulic oil path that relies on multiple rams and/or pump chambers of varying diameters and/or stroke. This method consists of many additional hydraulic unit components, is complex and expensive to manufacture and typically unreliable. Therefore a new design is desirable.
Accordingly, the primary object of the present invention is to provide a practical means of achieving a manually operated zero-load rapid lifting hydraulic jack having a lifting arm and a receiver integral to the lifting arm, wherein a lever can be inserted in order to accomplish the described quick no-load lift. With the lever engaged, a downward force applied to the lever forces the lifting arm upward to a position that enables contact of the lifting arm pad with the lift point. The receiver may be formed into the lifting arm as a manufacturing process or it may be welded or fixed by other attachment means. The configuration of the receiver may be of various forms; a receiving tube, a receiving hole, a receiving block, or any infinite variety of receiver configurations. The configuration of the receiver being secondary to the importance of the presence of a receiver to accept a lever of corresponding configuration which acts upon the receivers"" role as a fulcrum for the purpose of driving the lifting arm upward.
The various objects and advantages of the present invention will be more clearly understood from the following detailed description when read in conjunction with the appended drawings.